The executive at the Catalan club has reportedly played a key role in many of the club's biggest transfers in recent years, including the move which saw then-wonderkid Neymar arrive at the Camp Nou from Santos in 2013.
According to the aforementioned source, Sanllehi will become a part of the Arsenal board and work closely with chief executive Ivan Gazidis.
It was reported that he will become the new director of operations at the North London club and his job will be to help secure the club's top transfer targets.
Sanllehi is also credited with bringing Alex Sanchez and Luis Suarez to Barcelona, but his contract with the club expires later this year.
Dick Law resigned from his position as Arsenal's main transfer negotiator last month after a fairly disappoitining summer of transfer business.
Despite bringing in record signing Alexandre Lacazette, the Gunners failed to tie down either of their two key men, Alexis Sanchez and Mesut Ozil, down to new deals, as well has seeing multiple bids rejected for Monaco's Thomas Lemar.
Arsenal fans will be hoping Sanllehi's arrival can improve their fate during the transfer window.